Methanol and ethanol are useful industrial chemicals which may be used to make, inter alia, biodiesel. Ethanol is typically made commercially by the hydration of ethylene or the fermentation of starch. The ethylene is often obtained by steam cracking fossil fuels. Methanol is typically made by reacting carbon monoxide and hydrogen in the presence of a catalyst (the carbon monoxide and hydrogen often being generated in the synthesis of methane). There are problems with the methods described above. The synthesis of methane and hydration of ethylene rely on fossil fuel products, which may in the future become scarce and/or expensive. The fermentation of starch to produce ethanol can be expensive, depending on the price of the source of the starch (typically cassava).
There have been attempts to make ethanol and/or methanol from waste materials or by-products. One such waste material or by-product is glycerol. Glycerol is a by-product of the production of biodiesel and of the processing of vegetable oils. WO2009/130452 describes a method of making methanol in which a sugar alcohol (such as glycerol) is treated with high pressure hydrogen in the presence of a transition metal hydrogenolysis catalyst. The use of high pressure hydrogen gas may be undesirable, however, because hydrogen gas is explosive and the use of high pressures requires the use of containers which can withstand the pressures used.